CN106872174A - Automobile transmission rack Knock test engine transient cycle moment of torsion analogy method - Google Patents

Abstract

The invention discloses a method for simulating transient period torque of an engine in an automobile transmission bench knock test, comprising the following steps: 1) establishing an engine model of "throttle opening-speed-torque"; 2) establishing an inertia torque solution model to obtain Inertia torque T _I : At the same time, obtain the maximum magnitude of inertia torque A ₁ ; 3) Draw the dynamometer diagram to obtain the maximum magnitude of combustion torque A ₂ : 4) For the average torque T _M , the maximum magnitude of inertia torque A ₁ , and the combustion The maximum magnitude of torque A ₂ is used for fitting, while considering the number of cylinders of the simulated engine and the ignition advance angle Get the engine torsional vibration curve, that is, the total engine transient torque: The invention has high precision, high real-time performance and small calculation amount, and can satisfy the high dynamic control response during the simulation of engine transient cycle torque (torsion vibration).

Description

Simulation method of engine transient cycle torque for automobile transmission bench knock test

technical field

The invention relates to a method for simulating the performance test of an automobile engine, in particular to a method for simulating the transient period torque (torsional vibration) of an engine for an automobile transmission bench knock test.

Background technique

In recent years, the NVH problem of automobiles has attracted more and more attention from engineers. The periodic fluctuation of engine torque will cause torsional vibration of the drive train, which will generate noise and reduce the service life of parts. If the transmission gears are not properly designed, engine cycle torque ripple can cause transmission rattle, which can affect the NVH quality of the car. There are many disadvantages in using real engine to drive NVH test. 1) Engine fuel is flammable, and it is prone to fire and other dangerous factors during its working process. At the same time, the exhaust gas it emits is not conducive to environmental protection. 2) The NVH test mainly measures the noise problem of the transmission under test, and the higher noise of the actual engine in the test will affect the NVH test of the transmission. 3) In the initial stage of power train development, usually the matching engine is also being developed and tested, so it is difficult to obtain the engine as a drive to perform NVH and other performance tests on the power train on an indoor bench. To sum up, using a highly dynamic drive motor instead of an engine for indoor drive train bench tests has many advantages such as safety, environmental protection, and convenient testing.

If the NVH problem caused by periodic torsional vibration of the engine is to be reproduced on the indoor bench, a high-precision torsional vibration model (simulating the inertia torque of the piston connecting rod and the combustion torque of each cylinder) is required. The engine torsional vibration simulation system includes a drive motor with low inertia and high dynamic characteristics and a torsional vibration model that meets real-time control requirements (simulating the inertia torque of the piston connecting rod and the combustion torque of each cylinder). The periodic pulsation frequency of engine torque is very high. For example, if the idle speed of a 4-cylinder 2-stroke engine is 900r/min, its ignition frequency is 30Hz. It is also found that a complete cycle of torsional vibration waveform requires at least 12 points to be completely reproduced. , so to simulate the periodic torque vibration of the engine when the rotational speed is 900r/min, its communication frequency or control period must reach at least 30×12=360Hz; if the engine rotational speed is 6000r/min, its communication frequency or control period should reach 2400Hz, so the calculation speed of the engine model should meet the real-time control requirements. Accurate engine models have been discussed in many literatures, such as black-box models and models based on physical structures, etc., because these models require a large amount of engine development data or detailed engine design parameters, these parameters are not easy to obtain in drive train tests, and Traditional physical models are difficult to meet the requirements of high dynamic control response due to complex mathematical calculations when simulating engine combustion characteristics, so these models are not suitable for dynamic simulation of drive train benches. Therefore, it is urgent to provide an engine torsional vibration simulation method that meets the requirements of high dynamic real-time control.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for simulating the transient cycle torque of an engine in an automobile transmission bench knock test, which has high accuracy, high real-time performance, and a small amount of calculation, and can meet the requirements of the engine transient cycle torque simulation method. Highly dynamic control response during torque (torsional vibration) simulation.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is as follows: a method for simulating transient cycle torque of an automobile transmission bench knocking test engine is characterized in that: comprising the following steps:

1) According to the inherent parameters of the engine, the engine "throttle opening-speed-torque" model is established, through which the "throttle opening-speed-torque" model can obtain the corresponding torque according to the input throttle opening or speed signal signal, that is, to obtain the average torque T _M of the engine;

2) Establish the inertia torque solution model to obtain the inertia torque T _I :

The reciprocating inertial force generated by the reciprocating parts of the engine is:

In the formula: m is the total mass of the piston and connecting rod, x is the stroke of the piston, Indicates the piston acceleration;

Since the reciprocating inertia force acts on the crank pin through the connecting rod, a periodically changing moment is generated on the crankshaft, which causes the inertia torsional vibration of the shaft system, so:

In the formula, L is the length of the connecting rod, r is the radius of the crank, α is the crank angle, β is the angle between the center of the connecting rod and the crankpin and the rotation centerline of the crankshaft, and λ is the ratio of the crank radius to the length of the connecting rod;

Thus the piston acceleration (approximate formula) is obtained:

where _ωc is the rotational angular velocity of the crank;

The reciprocating inertial force is thus obtained as:

P _I =-mrω _c ² (cosα+λcos2α);

The moment produced by the reciprocating inertial force is:

Among them, the inherent parameters of the engine (m, L, r, α, β, λ, and ω _c ) are input into the inertia torque solution model according to the parameters of the engine to be simulated before the experiment;

At the same time, the maximum magnitude A ₁ of the inertia torque is obtained according to the inertia torque solution model;

3) Test the combustion pressure of the simulated engine on the engine test step, and measure the rotation angle of the crankshaft through the speed encoder at the same time; according to the operating data of the simulated engine under corresponding working conditions, the instantaneous cylinder working volume during the combustion process of the simulated engine is obtained; According to the instantaneous working volume of the cylinder and the corresponding combustion pressure, draw the dynamometer diagram to obtain the maximum amplitude A ₂ of the combustion torque:

4) Fit the average torque T _M , the maximum magnitude of inertia torque A ₁ , and the maximum magnitude of combustion torque A ₂ , and consider the number of cylinders of the simulated engine to calculate its inertia torque frequency f ₁ and combustion torque frequency f ₂ , while considering the ignition advance angle Obtain the engine torsional vibration curve, that is, the total engine transient torque T _en :

In the formula: t is the engine transient torque simulation period.

Further, when the engine is a multi-cylinder engine, first obtain the average torque, the maximum magnitude of the inertia torque and the maximum magnitude of the combustion torque through the above-mentioned method of step 1)-step 5), according to the engine inertia torque frequency, engine ignition combustion frequency and ignition The advance angle is fitted to obtain the total transient cycle torque of the engine.

Compared with prior art, the present invention has following advantage:

1. The present invention fits the engine average torque, the maximum magnitude of the inertia torque and the maximum magnitude of the combustion torque according to the engine inertia torque frequency, the engine ignition combustion frequency and the ignition advance angle, thereby obtaining the total transient cycle torque of the engine, each The mathematical model has a small amount of calculation, which saves system operation resources, has high accuracy and high real-time performance, and can meet the high dynamic control response during engine cycle torque pulse (torsional vibration) simulation.

2. The engine torsional vibration simulation method provided by the present invention can simulate the torsional vibration characteristics of the engine under different cylinder numbers, different crankshaft and flywheel moment of inertia, and is easy to be transplanted into different controllers, which better satisfies the high dynamic response of the bench control needs.

Description of drawings

Figure 1 is a schematic diagram of the structure of the test bench for the automobile drive train.

FIG. 2 is an engine torque MAP diagram.

Figure 3 is a schematic diagram of the engine piston structure.

Figure 4 is an engine diagram.

Figure 5. Schematic diagram of engine torsional vibration curve.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Embodiment: the present invention is mainly applied to the indoor automobile drive train test bench, and simulates the transient period torque (being torsional vibration) of the engine by driving the motor, and the goal is to provide a realistic engine working condition for the performance test of the drive train components such as the transmission Conditions, in order to achieve the purpose of performance testing of clutches, transmissions and other drive train components; and high accuracy, high real-time performance, can meet the high dynamic control response of engine cycle torque pulse (torsional vibration) simulation.

During specific implementation, such as: testing the transmission performance of the transmission in the knock test of the automobile transmission, the test bench is shown in Figure 1, which includes a host computer 1, a driver 2, a permanent magnet synchronous motor 3, an AC asynchronous motor 4, and a clutch , transmission 5 to be measured, encoder 6 and rotational speed torque sensor 7, wherein, permanent magnet synchronous motor 3 links to each other with the input end of transmission 5 to be measured by clutch, to drive transmission 5 to be measured; The output terminal of transmission 5 to be measured is connected to AC The asynchronous motor 4 is connected to the speed torque sensor 7 at the input and output ends of the transmission to be tested to collect test data, and the closed-loop feedback signals of the speed of the two motors are obtained by the encoder 6 installed on the two motors. In order to meet the requirements of fast-response closed-loop control, before the test, the physical size parameters of the engine and combustion parameters such as compression ratio are input. During the test, the engine torsional vibration simulation method of the automobile test bench is based on the input The real-time rotation speed and the accelerator pedal opening signal fed back by the encoder 6 calculate the total engine cycle torque pulsation target curve, and send it to the motor driver 2, and the motor driver 2 drives the motor to simulate the cycle torque pulsation of the actual working process of the engine. The drive train components provide a realistic engine cycle torque pulsation working environment, which is convenient for testing the NVH and other performance of the transmission under test on the indoor bench.

Referring to Fig. 2-Fig. 5, the transient cycle torque simulation method of the engine for the automobile transmission bench knock test includes the following steps:

1) According to the inherent parameters of the engine, the engine "throttle opening-speed-torque" model is established. The establishment of the engine "throttle opening-speed-torque" model is an existing technology. "MAP map is established. According to the "throttle opening-speed-torque" model, the corresponding torque signal can be obtained according to the input accelerator opening or speed signal, that is, the average torque T _M of the engine can be obtained.

2) According to the inherent parameters of the engine, the inertia torque solution model is established to obtain the inertia torque T _I :

The reciprocating inertial force generated by the reciprocating parts of the engine is:

In the formula: m is the total mass of the piston and connecting rod, x is the stroke of the piston, Indicates the piston acceleration;

Since the reciprocating inertia force acts on the crank pin through the connecting rod, a periodically changing moment is generated on the crankshaft, thereby causing the moment of inertia of the shaft system, and the piston stroke can be obtained by the following formula:

In the formula, L is the length of the connecting rod, r is the radius of the crank, α is the crank angle, β is the angle between the center of the connecting rod and the crankpin and the rotation centerline of the crankshaft, and λ is the ratio of the crank radius to the length of the connecting rod;

Thus the piston acceleration (approximate formula) is obtained:

where _ωc is the rotational angular velocity of the crank;

The reciprocating inertial force is thus obtained as:

P _I =-mrω _c ² (cosα+λcos2α);

The moment produced by the reciprocating inertial force is:

Among them, the inherent parameters of the engine (m, L, r, α, β, λ, and ω _c ) are input into the inertia torque solution model according to the parameters of the engine to be simulated before the experiment;

At the same time, the maximum magnitude A ₁ of the inertia torque is obtained according to the inertia torque solution model.

3) Test the combustion pressure of the simulated engine on the engine test step, and measure the rotation angle of the crankshaft through the speed encoder at the same time; according to the operating data of the simulated engine under corresponding working conditions, the instantaneous cylinder working volume during the combustion process of the simulated engine is obtained; According to the instantaneous working volume of the cylinder and the corresponding combustion pressure, draw the dynamometer diagram to obtain the maximum amplitude A ₂ of the combustion torque.

4) Fit the average torque T _M , the maximum magnitude of inertia torque A ₁ , and the maximum magnitude of combustion torque A ₂ , and consider the number of cylinders of the simulated engine to calculate its inertia torque frequency f ₁ and combustion torque frequency f ₂ , while considering the ignition advance angle Obtain the engine torsional vibration curve, that is, the total engine transient torque T _en :

Where: for a four-stroke engine, the frequency of moment of inertia = frequency of crankshaft × number of cylinders; frequency of combustion torque = frequency of crankshaft × number of cylinders/2;

In the formula: the crankshaft frequency is calculated from the crankshaft speed, and the crankshaft speed is measured by the speed encoder; t is the engine transient torque simulation period.

Because what the above-mentioned process obtains is the torque of the horizontal bar engine, therefore, when the engine is a multi-cylinder engine, first obtain the torque of each single cylinder through the above-mentioned method of step 1)-step 4), and then perform torque superposition according to the number of cylinders and firing sequence, In order to obtain the total torque signal of the engine.

The engine torsional vibration signals on the existing drive train bench are generally provided by engine models based on physical structures. Since these models require a large amount of engine development data or detailed engine design parameters, these parameters are not easy to obtain in the drive train bench test, and Traditional physical models are difficult to meet the requirements of high dynamic control response due to complex mathematical calculations when simulating engine combustion characteristics, so these models are not suitable for engine torsional vibration simulation of drive train bench. And the engine torsional vibration simulation method of the present invention divides engine torque into average torque, inertia torque and combustion torque, thereby carries out mathematical model solution to average torque, inertia torque and combustion torque respectively, and each mathematical model calculation amount is small, thereby It effectively saves system operation resources, and solves the real-time and dynamic response requirements of the torsional vibration model during the engine cycle torsional vibration simulation process.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit the technical solutions. Those skilled in the art should understand that those who modify or replace the technical solutions of the present invention without departing from the present technology The purpose and scope of the scheme should be included in the scope of the claims of the present invention.

Claims (2)

1. a kind of automobile transmission rack Knock test engine transient cycle moment of torsion analogy method, it is characterised in that：Including such as Lower step：

1) according to the intrinsic parameter of engine, engine " accelerator open degree-rotating speed-moment of torsion " model is set up, " throttle is opened by this Degree-rotating speed-moment of torsion " model can obtain corresponding torque signal according to the accelerator open degree or tach signal of input, that is, obtain Obtain the average torque T of engine_M；

2) set up inertia moment of torsion and resolve model, obtain inertia torque T_I：

Reciprocal inertia force produced by engine reciprocations moving component is：

$P_I=-m\stackrel{\·\·}{x};$

In formula：M is the gross mass of piston and connecting rod, and x is piston stroke,Represent piston acceleration；

Because reciprocal inertia force is acted on crank-pin by connecting rod, periodically variable torque is produced on bent axle, so as to draw The Inertia Torsional Vibration of shafting is played, therefore：

$\begin{array}{c}x=(L+r)-(Lcos\mathrm{\β}+rcos\mathrm{\α})\\ =r(1-\cos \mathrm{\α})+L(1-\sqrt{1-{\mathrm{\λ}}^2{\sin }^2\mathrm{\α}})\end{array};$

L is length of connecting rod in formula, and r is throw of crankshaft, and α is crank angle, and β is connecting rod and crank pin center and bent axle pivot The angle of line, λ is throw of crankshaft and length of connecting rod ratio；

So as to obtain piston acceleration (approximate formula)：

$\stackrel{\·\·}{x}={{\mathrm{r\ω}}_c}^2(cos\mathrm{\α}+\mathrm{\λ}cos2\mathrm{\α});$

ω in formula_cIt is crank rotation angle speed；

Thus obtaining reciprocal inertia force is：

P_I=-mr ω_c ²(cosα+λcos 2α)；

Torque as produced by reciprocal inertia force is：

$\begin{array}{c}{T}_I=P_I\frac{sin(\mathrm{\α}+\mathrm{\β})}{\cos \mathrm{\β}}\·r\\ \≈-{\mathrm{mr}}^2{{\mathrm{\ω}}_c}^2(\cos \mathrm{\α}+\mathrm{\λ}\cos 2\mathrm{\α})(sin\mathrm{\α}+\frac{\mathrm{\λ}}{2}sin2\mathrm{\α})\\ ={\mathrm{mr}}^2{{\mathrm{\ω}}_c}^2(\frac{\mathrm{\λ}}{4}\sin \mathrm{\α}-\frac{1}{2}sin2\mathrm{\α}-\frac{3\mathrm{\λ}}{4}sin3\mathrm{\α}-\frac{{\mathrm{\λ}}^2}{4}\sin 4\mathrm{\α})\end{array};$

Wherein, engine intrinsic parameter (m, L, r, α, β, λ and ω_c) ginseng of engine simulated as needed before experiment Number is input in inertia moment of torsion resolving model；

Meanwhile, model is resolved according to inertia moment of torsion and obtains inertia torque maximum amplitude A₁；

3) test is modeled engine combustion pressure on Engine Block Test step, while measuring bent axle by rotating speed coder Corner；According to service data of the engine under correspondence operating mode is modeled, obtain being modeled instantaneous in engine combustion process Displacement；According to instantaneous displacement and corresponding combustion pressure, indicator card is drawn, obtain combustion torque maximum Amplitude A₂：

4) to average torque T_M, inertia moment of torsion maximum amplitude A₁, and combustion torque maximum amplitude A₂It is fitted, while considering The number of cylinders of engine is modeled, its inertia moment of torsion frequency f is calculated₁, combustion torque frequency f₂, while considering electronic spark advance AngleObtain engine torsional oscillation curve, i.e., total engine transient torque T_en：

In formula：T is engine transient moment of torsion simulation cycle.

2. automobile transmission rack Knock test engine transient cycle moment of torsion analogy method according to claim 1, its It is characterised by：When engine is multicylinder engine, first by step 1)-step 5) above method obtains average torque, used Amount moment of torsion maximum amplitude and combustion torque maximum amplitude, according to engine inertia moment of torsion frequency, engine ignition combustion frequency It is fitted with ignition advance angle, the transient state cycle moment of torsion total so as to obtain engine.